High average power (HAP) solid state laser (SSL) systems are known. They are becoming increasingly important in both defense and commercial applications. Much of the recent growth in the popularity of SSL systems can be attributed to the introduction of pumping by laser diodes.
As those skilled in the art will appreciate, diodes are inherently very efficient in converting electric energy into pump light. Thus, diodes deposit only a comparatively small amount of waste heat into the solid state medium. Advantages of diode pumped SSL systems with respect to gas lasers include all electric operation, short wavelength, compatibility of optical fibers, continuous duty, high efficiency, and the prospect of engineering a high power device having a comparatively small and lightweight package.
Emerging military and industrial applications for HAP SLL systems required the integration of laser systems on mobile platforms such as trucks, ships, and aircraft. More particularly, there is a strong need for 100 kW class HAP SSL systems for use in air defense and precision strike. Air defense applications for HAP SSL include defense against tactical and strategic missiles. HAP SSL systems are also used worldwide in industrial applications, such as in cutting and welding tools for use in the automotive, aerospace, appliance, and shipbuilding industries.
Solid-state lasers utilize electrical pumping, such as by the use of highly efficient semiconductor diodes. Despite the use of such electrical pumping, the operation of SSL systems still produces a significant amount of waste heat that must be rejected. Typically, for each joule of laser energy produced, three to four joules of heat must be removed from a SSL system and then rejected to the environment.
Rejecting waste heat from a SSL system into an environment that is at the same or higher temperature with respect to the SSL system inherently necessitates the use of refrigeration in order to pump the heat from laser components into the environment. A variety of cooling systems of this type are commercially available and currently used in many applications. Indeed, closed loop cooling systems are commonly used with contemporary SSL systems. However, such closed loop cooling systems tend to be undesirably bulky and heavy in comparison to the SSL system that they support.
The size and weight of the refrigeration system is not of particular concern in fixed laser installations, e.g., factory installations. However, such closed loop refrigeration systems are entirely unsuitable for use in large, e.g., multi kW, SSL systems that are installed upon mobile platforms where size and weight are paramount.
Furthermore, producing the very high flow rates (hundreds of gallons per minute) required to support high energy SSL lasing requires the use of very large pumps that are typically electrically operated. These pumps can require 20%-30% of the SSL system's electric power budget.
Furthermore, such pumps generate substantial flow vibrations that can have a wide band spectrum. The wide band spectrum tends to find resonances in coolant lines and structures. These resonances tend to undesirably perturb the alignment of laser components.
Thus, contemporary cooling systems for high average power solid state laser systems suffer from inherent disadvantages that tend to detract from their overall desirability and effectiveness. For example, contemporary cooling systems tend to be undesirably bulky, heavy, and costly. They also tend to generate excessive flow vibration, particularly at the high flow rates that are required to provide effective cooling.
In view of the foregoing, it is desirable to provide a lightweight, compact, low cost thermal management system for a high energy solid state laser (SSHEL) weapon. It is further desirable to provide such a thermal management system that has very quiescent flow of coolant at the flow rates required for effective cooling. Such a thermal management system would facilitate the construction of more powerful and more economical high average power solid state laser systems.